A Liquid Crystal Display (LCD) has been widely used due to its advantages such as thin volume, lightness and low electromagnetic radiation. A configuration of a LCD panel is as shown in FIG. 1, which comprises a display panel (an array substrate 101, a color film substrate 102 and the liquid crystal), a data driving integrated circuit (Data IC) 103, a gate driving integrated circuit (Gate IC) 104, a Flexible Printed Circuit Board (FPC) 105 and a Printed Circuit Board (PCB) 106. Its operation principle is as follows. Signals output by the system (such as a Transistor Transistor Logic (TTL)/Low-Voltage Differential Signaling (LVDS), and so on) enter the Data IC and a power unit via a connector on the PCB so as to generate signals that the Gate IC and Data IC can recognize, including a synchronous signal, an analog signal Gamma voltage and a digital signal (TTL/mini-LVD), etc. These signals will be output to the LCD panel after being processed by the Gate IC and the Data IC, so as to control the liquid crystal panel to display.
The Gate IC essentially is a shift register, and its main function is to perform a progressive scan on the liquid crystal panel. The Data IC essentially is a digital-to-analog converter (DAC), and its main function is to convert the digital mini-LVDS signal generated by a Timing Controller (T-con) into an analog signal corresponding to the gray scale voltage by using a Gamma voltage output on the PCB and input the same to the LCD panel, as shown in FIG. 2.
The above Gamma voltage is generated by a Gamma reference voltage generation circuit, and the Gamma reference voltage generation circuit is designed based on an ideal gray scale-voltage (L-V) curve. However, in practice, due to effects of various factors such as a gravity, a process uniformity, a path loss, a backlight uniformity and so on on the display panel, although the Gamma reference voltage generation circuit may improve a display effect of the display panel, the actual display effect of the fabricated display panel usually cannot reach an ideal display effect.
For the LCD, the voltage (V) between an upper plate and a lower plate of the LCD panel does not have a linear relationship with a light transmittance (T); therefore, in order to correct this variation, it is necessary to change a voltage output by the Data IC. The Data IC essentially is the digital-to-analog converter, and its output analog voltage is determined by the Gamma voltage and corresponding gray scale bit(s). However, the gray scale bit(s) is a fixed value, so it can only change the Gamma voltage in order to change the output voltage. Therefore, when a pixel data of a digital picture to be displayed is to be converted into the voltage signal input to two sides of the liquid crystal, an action of tuning the Gamma voltage must be performed to relieve a display non-uniformity and a color cast phenomenon.
When the generation of the Gamma voltage is realized by voltage distribution of a Gamma resistor string as shown in FIG. 3, it is possible to tune the voltage of the Gamma resistor series to perform Gamma tuning.
When the generation of the Gamma voltage is realized by a programmable Gamma device as shown in FIG. 4, assuming that the display panel has a uniform brightness of the display under different gray scales, it is possible to test the brightness at a center point of the display panel and tune the Gamma voltage by using test values. When such a method is used to tune the Gamma voltage for small size LCE panels, since the influences of the gravity, the process uniformity, the path loss, the backlight uniformity on it are negligible (the small size LCD panels can be regarded to have the uniform process and the uniform backlight), the picture display has a good uniformity after Gamma tuning is performed by using such a method. However, for large size LCD panels, since the influences of various factors such as the gravity, the process uniformity, the path loss, the backlight uniformity and so on are not negligible, when the above method is still used to perform the Gamma tuning, phenomenons of the display non-uniformity and color cast in the picture display would occur in the LCD panel.